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A TEXTBOOK OF PHYSIOLOGY 



but little; one much carbohydrate, another but little. Their chemical 

 nature in part determines the rate at which these bodies are split off 

 from the protein ingested. Therefore, early in digestion there is 

 a beginning of the sorting out of the special constituents of the 

 different proteins a sorting out to enable the body to choose the 

 portions of the ingested protein requisite for the building of its own 

 special proteins. In digests made in the test-tube, the maximum of 

 hetero- and proto-proteose occurs in half an hour, and then rapidly 

 diminishes. One form of secondary proteose (B) showed similar 

 variations. A gave its maximum in five to eight hours, C after two 

 or three days, peptone in one to two months. Of the contents of a 

 dog's stomach, after half to six hours' digestion of cooked meat, 

 90 per cent, consisted of proteoses, acid metaprotein accounting for 

 the other 10 per cent. The peptones and peptides are absorbed as 

 soon as they are formed in the stomach. Normally, this absorption 

 is from 20 to 30 per cent, of the protein eaten. The toxin of 

 protein-like bodies for example, of tetanus. and of snake venom 

 is rendered innocuous by gastric digestion. 



Peptic digestion in the same period does not break down the 

 protein &o far as tryptic digestion. The fact that with prolonged 

 gastric digestion in vitro all the end products of tryptic digestion are 

 formed, except the hexone bases, would seem to afford support to the 



